Synthetic drugs such as chemotherapeutic agents or immunotherapeutic agents have been heretofore widely used as anti-tumor agents. However, these drugs generally encounter problems that their specificity is low and side-effects are serious. On the other hand, many tumor cell growth inhibitors have been found in tissue culture cells. These inhibitors could be such anti-tumor agents that would be highly specific and would have minimized side-effects. Representative examples of such inhibitors are interferon, lymphotoxin and tumor necrosis factor (TNF). Recently, a tumor cell cytotoxic factor obtained from human fibroblast and a tumor cell growth inhibitor obtained from human lung cancer cells are reported in Japanese Patent KOKAI Nos. 1-148197 and 1-187094, respectively.
Some cell growth inhibitors are isolated also from the fibroblastic 3T3 cell line established from the cells obtained from Swiss fetal mice. For example, Natraj et al. has reported that a growth inhibitor was obtained from the cell surface of 3T3 cells in the stationary phase, cf., Proc. Natl. Acad. Sci. U.S.A., 75, 6115-6119 (1978). Harel et al. has reported that a growth inhibitor having a molecular weight of 40 kDa was obtained from the culture supernatant of 3T3 cells, see J. Cell. Physiol., 119, 101-106 (1984), ibid., 123, 139-143 (1985). However, these growth inhibitors all fail to show any significant inhibitory action against tumor cells, as is known in the art.
The present inventors previously succeeded in isolating, from the culture supernatant of 3T3 cell-derived cell line, novel tumor cell growth inhibitors having an activity of inhibiting the growth of tumor cells, which was filed as Japanese Patent Application No. 3-11950.
The tumor cell growth inhibitors exhibit a potent growth inhibition activity against human promyelogenous leukemia cells or human uterine cervical cancer-derived cells and are expected to be effective for the treatment of cancer.
For use as new carcinostatic agents, it is required to supply the tumor cell growth inhibitors in a sufficient amount. It is thus desired to develop a method for production available with industrial advantages.